The evil Lydia, played by Ann Dowd on the Hulu series, may walk softly and quote scripture, but cross her or defy her and she’ll zap you with her handy cattle prod.

On the chilling series, adapted from Margaret Atwood’s 1985 novel, Lydia is truly evil — the woman who serves her masters by oppressing and torturing other women. As played by the lethally calm Dowd (“The Leftovers”; “Masters of Sex”), she’s one of this year’s scariest characters on TV.

The women on “The Handmaid’s Tale” live in the post-apocalyptic republic of Gilead in what’s left of the United States. Ruled by the male Commanders, women fulfill one function: to bear children. They are not allowed to own property, have their own money or even read. Like slaves, the women of childbearing age take their names from the men to whom they belong. Aunt Lydia indoctrinates them at the Rachel and Leah Education Center. She tells bewildered new captives like Offred (Elisabeth Moss) and obedient handmaids alike “Fertility is a gift from God” in a world where the birth rate has plunged due to the heavy use of contraceptives.

She also presides over childbirth, as midwife in a bizarre public ceremony in which the Commander’s wife, sitting behind the pregnant handmaiden, simulates labor pains while the young woman pushes the child out.

As Gilead’s behavior cop, Aunt Lydia enjoys certain privileges denied to the handmaids or even the Commander’s wives: like the other Aunts, women beyond childbearing age, she can publicly read and write. Although the wives are not allowed to punish the handmaids, Aunt Lydia is ready to spring into action. In the first episode, she zaps Janine (Madeline Brewer) for a moment of impertinence with a lethal warning — “Blessed are the meek” — and later has Janine’s eye plucked out. When Offred helps another handmaid escape, Aunt Lydia stands by while the soles of her feet are lashed. In the series’ most frightening scene, a rebellious and gay young woman (or “gender traitor”), Ofglen (Alexis Bledel), is muzzled and subject to genital mutilation. When she wakes up from anesthesia and stares at her bandaged crotch, Aunt Lydia is there to greet her. “You can still have children of course, but things will be so much easier for you now,” she says. “You won’t want what you can’t have. Blessed be the fruit, dear.”

Ofglen’s bloodcurdling scream will echo in your soul.

There have been mean women on TV, like the pathological First Lady Claire Underwood on “House of Cards” — Robin Wright’s glacial beauty somehow makes the cruelty less painful (and more predictable) — and diabolical women in the movies, like Nurse Ratched (Louise Fletcher) in “One Flew Over the Cuckoo’s Nest.

But in her false maternalism and hypocritical piety, Aunt Lydia takes things to an insidious new level as every woman’s worst nightmare.